In industrial communications, deterministic/stochastic guarantees may be needed for their end-to-end real-time requirements. To provide this, corresponding systems may use specialized forwarding hardware. In order to lower the cost of real-time communication systems, a centralized control plane mechanism may be used to provide Quality of Service (QoS) guarantees with off-the-shelf packet-switched Ethernet hardware.
Another approach is a function split concept which separates the resource allocation (e.g. buffer size and data rate) and the routing of a flow (real-time flow embedding) as two distinct sub-problems. Both, the resource allocation and the flow routing, are done on a queue-level basis. This means that a queue-level topology is used which defines queues per link. Resource allocation is done for each link of the queue-level graph and routing is done on the queue-level graph. That is, resources are allocated to queues and the routing of a flow consists in both choosing the physical links followed by the flow and, for each link, the queue at which the flow will be buffered. In order to be able to compute worst-case delays, a particular reservation of resources at the network queues is needed. As a result, the flow embedding relies on a resource-based access control mechanism, i.e. a mechanism deciding whether or not enough resources are still available at a queue in order to route a new flow through this queue. As multiple resources (e.g. buffer and data rate) influence the delay of a queue, solving the resource allocation problem in an optimal way is very challenging.